Transition Metal Nitrides for Electrocatalytic Application: Progress and Rational Design

Ab initio electronic structure analysis of ground and excited states of HfN0,

High-level ab initio electronic structure analysis of third-row transition metal (TM)-based diatomic species is challenging and has been perpetually lagging. In this work, fourteen and eighteen electronic states of HfN and HfN+ respectively are studied, employing multireference configuration interaction (MRCI) and coupled cluster singles doubles and perturbative triples [CCSD(T)] theories under larger correlation-consistent basis sets. Their potential energy curves (PECs), energetics, and spectroscopic parameters are reported. Core electron correlation effects on their properties are also investigated. Chemical bonding patterns of several low-lying electronic states are introduced based on the equilibrium electron configurations. The ground state of HfN (X2Σ+) has the 1σ22σ23σ11π4 electronic configuration, and the ionization of the 3σ1 electron produces the ground state of HfN+ (X1Σ+). Ground states of both HfN and HfN+ are triple bonded in nature and bear 124.86 and 109.10 kcal mol-1 binding energies with respect to their ground state fragments. The findings of this work agree well with the limited experimental literature available and provide useful reference values for future experimental analysis of HfN and HfN+.

Composition and Morphology Modulation of Bimetallic Nitride Nanostructures on Nickel Foams for Efficient Oxygen Evolution Electrocatalysis

Metal-nitrides-based electrocatalysts for efficient oxygen-evolution have been extensively studied as one of the most promising candidates to fulfil the demand for future energy-conversion and storage. Herein, a series of NixCo1−xO- and NixCo1−xN-based nanostructures on nickel foams were reported to show excellent activities for oxygen-evolution reaction. The catalysts were prepared and modulated rationally via a facile-hydrothermal method, followed by high-temperature calcination under air or nitrogen atmosphere. The optimal bimetallic-nitride catalyst Ni0.3Co0.7N shows a small overpotential of 268 mV at 20 mA cm−2, and a Tafel slope of 66 mV dec−1 with good stability. The enhanced OER-performance is ascribed to the synergetic effect of the unique morphology and the intrinsic catalytic property of the nanostructure after nitridation.